Heat shock proteins (HSPs) are a group of highly conserved polypeptides involved in cellular response to heat or other physical or chemical stresses. It has been recently reported that HSPs could play a role in cellular differentiation. In this study we have evaluated, by a cytofluorimetric method, the presence of HSP-70 in HL-60 cells during treatment with all- trans retinoic acid (ATRA), 9-cis retinoic acid (9-cis RA), and 13-cis retinoic acid (13-cis RA). After 1 and 3 days of incubation at 10-7 M, HSP- 70 did not show any variation compared to control; prolonging the exposure, together with the appearance of cellular differentiation along the granulocytic pathway and apoptosis, a progressive decrease of HSP-70 was observed that, after 8 days of treatment, was reduced by 40% with ATRA and by 28% with 9-cis RA compared to untreated samples, while only minimal changes were evident by incubating the cells with 13-cls RA. Reduction of HSP-70 was not associated with decreased protein synthesis, as demonstrated by [3H] leucine incorporation. Double labeling with propidium iodide showed a decrease in HSP-70 in all the phases of the cell cycle concomitant with a reduced percentage of cycling cells in ATRA-treated samples. Dot blot and Northern blot analysis demonstrated no change in HSP-70 mRNA after retinoid treatment, thus suggesting a post-transcriptional regulation of the phenomenon. This reduced production of HSP-70 caused by ATRA and by 9-cis RA, though to a lesser extent, could render the cells more sensitive to cytotoxic agents and could provide the rationale for the efficacy of ATRA + chemotherapy combinations.
CITATION STYLE
Tosi, P., Visani, G., Ottaviani, E., Gibellini, D., Pellacani, A., & Tura, S. (1997). Reduction of heat-shock protein-70 after prolonged treatment with retinoids: Biological and clinical implications. American Journal of Hematology, 56(3), 143–150. https://doi.org/10.1002/(SICI)1096-8652(199711)56:3<143::AID-AJH2>3.0.CO;2-Y
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